1. Technical Field
The invention relates to the routing of requests to a networked server in a computer environment. More particularly, the invention relates to determining a dynamic hop count between two nodes across a network in a computer environment.
2. Description of the Prior Art
The Internet is a confederation of loosely connected networks that connect computers all around the world. The proliferation of information and immense user population has made the management of information critical. Information is mirrored on multiple servers in order to improve performance, availability, and scalability.
To facilitate the mirroring of information, clients requesting information need to be routed to the optimal server. The traffic management industry routes traffic to the optimal server using different latency metrics including the Round Trip Time (RTT) and hop count. The Round Trip Time measures the time it takes for a packet to travel between a server and a client or another server.
The dynamic hop count between a client and a server is typically derived from the Border Gateway Protocol (BGP). BGP is specified in RFC 1267 published in October 1991 and RFC 1654 published in July 1994. BGP gives the hops between different Autonomous System Numbers (ASN). The dynamic hop count can be used to differentiate latency metrics that might be close in terms of RTT.
The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems. The network reachability information includes information on the Autonomous Systems (AS) that the reachability information traverses. A BGP speaker advertises to its peers, i.e., other BGP speakers that it communicates with, in neighboring ASs only those routes that it uses. The information is sufficient to construct a graph of AS connectivity from which routing loops may be pruned.
Determining the dynamic hop count is currently problematic due to the following reasons:                1. BGP hops: The actual number of hops will typically be larger than that advertised by the BGP protocol since BGP only gives the hops between the ASNs.        2. IP hops: Getting hop counts from the Internet Protocol (IP) is difficult because the Time To Live (TTL) field that is part of the IP header is not initialized to standard values by the various TCP/IP stack software running on various Operating Systems, e.g., Windows 98, Linux, NT, etc.        
The invention described in this patent provides a different and more precise method of determining the dynamic hop count.
It would be advantageous to provide a method and apparatus for determining latency between multiple servers and a client that provides a more precise method of determining dynamic hop counts. It would further be advantageous to provide a method and apparatus for determining latency between multiple servers and a client that reduces the traffic required to measure the hops across the network.